This invention relates to a material for the treatment of liquid systems which have foaming properties and more particularly to an improved defoamer.
Foaming or frothing is frequently encountered at the surface of liquids due to the entrapping of gases, such as air. This foaming especially occurs when the liquid is heated under reduced pressure or when agitated. The textile, paint and paper industries are some of the activities where typical foaming problems are encountered.
Defoamers, which, when added to a foaming liquid, break down or inhibit the formation of bubbles in the foam, are, of course, old in the art. Some of these defoaming compositions are an admixture of components such as organosiloxane polymers, including silicone oil, and/or normally hydrophilic materials which have their surfaces treated hydrophobic, such as silica.
One of the problems with these old compositions is that their effective shelf lives are relatively short, because a "settling out" of the various components, such as the silica, occurs. Before it can be used, the defoamer usually then has to be agitated, as in a mechanical shaker, so that the components can again be in an intimate admixture.
Another problem which effects the effective shelf-life of these silica-based defoamers is their sensitivity to water. Although the normally hydrophilic or water loving silica is treated to be predominantly hydrophobic or water repelling before it is used in a defoaming compositon, nevertheless, some of the silica is still hydrophilic in nature. As a result, when water enters the silica based defoaming composition, the hydrophilic silica is attracted to the hydroxyl groups of the water molecules causing a settling out of the silica from the mixture. The composition has to be agitated to break up the complex formed by the silica and the water.
Pure organic defoamers have been produced in the past, but they have been found to be ineffective in that they require a large amount of the defoaming agent to accomplish the defoaming process.
The silica based defoamers are expensive, because such a large amount of silica or other expensively treated particles are used in the compositions.